Thanks. I now think that Mono would be a better choice. As we only do Integration and azure related stuff. So most of the code will be dependent on each other and reusable.
Is it also better if we have to use some open source dependency at multiple places?
Going multi first is just too annoying to manage and doesn't make much sense. Also, it's more repos you have to get running on your device, and more room for divergence.
It gets even worse when small companies insist on creating their own packages...
Also, I usually have a repo that is for deployment-focused stuff, like kubernetes configs. These are good reasons. I think maybe a "scripts" or "scratch file" or a mix of the two can also be its own repo, for stuff that doesn't really belong anywhere specific and isn't getting called by other code.