Control Remote Mac/PC Solution?

[Das Goravani]

Hello $all,

I know this has been discussed, but it usually goes over my head. 

I am wondering if I could be told by those experienced with the same:

What is the/a solution for controlling remote Macs or PC’s in order to do tech support, or teach a user something.. 

I don’t need this very often.. in fact very rarely. So I’m thinking if there is a free solution. I can put up with ads if need be.

I know by now Grandma knows the answer to this question, but I do not. 

I have never controlled a remote computer. Someone has controlled mine using TeamViewer one time.

I use a Mac as MY computer.. so I would be controlling other Mac, or PC, from a MacBook Pro. BigSur. Plenty of RAM. 

I have looked at some and the subscription fees are huge compared to my need, which is rare, perhaps a few times a year. 

Ideally the user on the remote end need not install anything. That would be ideal. But if they must, then they must. 

Thank you,

Das Goravani