Yeah, you got it, you can now use the modern script editor web part as a poor mans solution to bootstrap applications as a Teams tab. And the better approach is to develop a real Teams tab application – just so you know!
I did not really intent to do this, but I had a request to update the web part to SPFx v1.10.0 as some people have issues building SPFx v1.4.1 on their machines. While upgrading I figured I’d do a revamp so I updated the web part with a proper html editor and enabled Teams tab support as well – because why wouldn’t you right? (A shoutout to the PnP team for suggesting this).
Check out the readme from the below link if you want to test the Teams tab support as you need to edit some default settings to make that happen.
