We created an asp.net core webapp hosted as Azure App Service with app service authentication. In App Studio we set up a personal tab and distributed the app as enterprise app. For all users the app is working without problems in the Teams Web App, but for some users it's not working in the desktop app. If those users use the app the tab does not display anything.
We tried to cleanup the Teams App and also re-installed the Teams Desktop App but with no success. The log in Azure shows only one entry if the user tries to connect the custom app (XXXX is blanked out hosted web app):

2020-07-29T06:33:46 PID[32324] Information Redirecting: https://login.windows.net/78dbf809-648b-40d8-a0a1-17249b3065ca/oauth2/authorize?responsetype=idtoken&redirecturi=https%3A%2F%2FXXXXXX.azurewebsites.net%2F.auth%2Flogin%2Faad%2Fcallback&clientid=b93bdff9-599c-458a-9d5f-86f0e4a51225&scope=openid+profile+email&responsemode=formpost&nonce=919fd712db1b4da9a1ca92c6eaf7ffd2_20200729063846&state=redir%3D%252F

Users with a working app do not get this entry. As soon as we switch off authentication, the app starts working.

I'm in the process of converting several existing web parts (built in Visual Studio using the SharePoint Add-In project template) to work in Microsoft Teams. In a nutshell, there are 2 routes to accomplish this:

(1) Using SharePoint Framework (SPFx), NodeJS, Typescript, visual Studio Code and Yeoman generator, OR
(2) Visual Studio, HTML, Javascript, AppStudio for Microsoft Teams and NGROK (for testing).

Following option (1) solves this whole issue completely, because it only involve these steps to make the app part available in both SharePoint AND Teams:
1. Ensure that the supportedHosts config setting in <WebPart>.manifest.json has the "TeamsPersonalApp" and "TeamsTab" options included.
2. Execute gulp bundle --ship in Command Prompt.
3. Execute gulp package-solution --ship in Command Prompt.
4. Drag-and-drop the resulting package onto the Sharepoint App 5. Catalog and wait for the upload to complete.
6. Click on the "Sync to Teams" menu item.

However, option (1) does not work for me, because the web part uses DevExtreme controls that is built in JavaScript, and the DevExpress development/support teams are not familiar with using their controls in a web part that is being built in SPFx. In addition, the web part uses API calls to retrieve data.

So, I completed the development of one of the web parts using option (2). These are the resources I referenced to do the development:
* https://www.rickvanrousselt.com/teams-ramp-up-part-3/
* https://docs.microsoft.com/en-us/microsoftteams/platform/tutorials/get-started-dotnet-app-studio.

As it stands, it works very nicely. However, this web part must be available in SharePoint as well. The problem is that the schema of the manifest.json files of options (1) and (2) differs, so SharePoint will not allow the .zip file that is generated with option (2) to be uploaded.

I came across this page, but there are many broken links on the page and it doesn't really answer the question: https://techcommunity.microsoft.com/t5/microsoft-teams/is-it-possible-to-create-a-teams-webpart-and-display-it-on/m-p/110476.

If anyone could provide help with this (additional links, insights, etc), I'd really appreciate it!

Expected Flow:

1) Host user schedules meeting in Teams and includes all parties (other @company.com users, @something.onmicrosoft.com HoloLens Remote Assist account, and any other external parties needed).
2) Everyone joins the scheduled meeting and the Host will “ask to join” on the @something.onmicrosoft.com HoloLens Remote Assist user listed in the “others invited” section of People Pane. There is no email setup on these accounts – so we don’t have the luxury of “Join Meeting” on Remote Assist app.
3)HoloLens user receives an incoming call and can join with video.

However - this is inconsistent. Often the HoloLens account (@something.onmicrosoft.com) is not available to 'ask to join' in the people pane. When this happens we have no ability to invite the users because they are outside of the tenant.

On a public team meeting the accees page should be change :
1. The connect button is change to indicate that you need a team licences AND the anonymous link is promoted to a buttons and is evident
2. As there is free team licence now, remove the requirement to have a team licence to be able to connect and allows any account to complete the authentification.

Ideally option 2 will be the best at it will allows us to know who joint or ask question. We can event have a public live event that required a authenticate account (google, Microsoft or one time password acces)

This need to be fix, we have live event plan and as people get stuck in a infinite loop is they try to connect and the fact the anonymous link is not evident and the fact there is no error return to the end user we had test pilot person that tryptophan login during 10 minutes.

I can't use Teams with touch enabled devices on windows. Either kill touch devices for windows or provide a client capable of using touch input. Scrolling in the files tab does not work with touch for surface Book surface Go or any touch enabled device. Teams is a new product. If new Microsoft products do not use new features in windows stop selling more expensive touch devices, eliminate touch API or make a product that uses HW features described as being the future.

This Windows OS as second class citizen approach only means stop developing on windows and stop caring about windows is devices