Been using them for years.

It’s completely free, open source and has:

• Unsupervised (for headless servers) or supervised (helping out relatives) access
• Easily file transfers
• Cross-copy paste
• Identification server (what gives out connection IDs) can be self-hosted or you can use theirs for free
• Can control PCs from mobile app (though not vide versa)
• Experimental web browser client.