I heard Paul talking last week on Windows Weekly about using Notepad to strip text of all formatting, etc. and to make it plain text. I have used Notepad for that same reason among others for many years too.
I stumbled across a tiny, but very useful app on the Microsoft Store in Windows 10 last year, called PureText. The app simply strips copied text of all formatting and creates plain text. The app has worked fine for me.
The Microsoft Store version (https://www.microsoft.com/en-us/p/puretext/9pkjv6319qtl) is 396 KB, way bigger than the 64-bit desktop version of 43 KB you can get directly from the dev (ttps://stevemiller.net/PureText/), but I still choose to just use the Store version knowing it can be updated without me having to do it manually.
In the app, I set up the hotkey combination CTRL + ` (the accent mark below the tilde on the key below the Esc key) so I can do the combination easily with one hand and that combination doesn’t interfere with any other software I’m running.
Check it out and I hope it helps.