Problem: You have an old XP (!) or Windows 7 box. Teamviewer no longer supports your OS, and/or is endlessly bugging you with "Commercial Use Detected!" nag-boxes.
Solution: Try AnyDesk.
• It's free.
• It has a portable version - you can try it without installing a thing.
• It works on old operating systems (including XP (!))
• It's pretty nice.
Some features are pay-only, any the subscriptions ain't cheap. But, so far, I've not found anything the free version lacks that I need.
This saved a very old PC of mine after Teamviewer stopped supporting old boxen. I need this ancient PC to run a prehistoric printer, with neither being supported by newer software. AnyDesk saved it when Teamviewer stopped connecting in v15.