I am having the exact same issue as the OP.
My girlfriend bought Minecraft for PC, running on Windows 10.
I can see her world from my Switch while she’s playing and it says the world is joinable. She’s even sent me an invite from PC and it showed up on my Switch. But the connection to her PC world is never made. Exactly like OP says: “Eventually an error is returned that the world cannot be joined and the connection timed out.”
I’ve tried disabling the firewall, making sure Minecraft is whitelisted within the firewall settings, I’ve uninstalled third party antivirus software, I’ve tried port forwarding, and I’ve tested wifi vs wired connection. All come back with the same result: connection times out.
Any advice or some insight into whether there’s a larger problem would be much appreciated.
I play with my girlfriend a lot. We don’t use realms. She has a world on her Switch and I come into it via my own Switch. Since 1.18.30 and 1.18.31, whenever the game is experiences the autosave freeze bug, I’m almost always disconnected from her game and sent back to the menu. I’ll reconnect to her game easily enough once it has unfrozen, but I’ll just be disconnected again on the next autosave. As you can imagine, playing together has been very frustrating the last couple weeks as a result.
Just adding another comment to back-up Alejandro Cruz’s issues. I tried connecting to my girlfriend’s Windows 10 world from my PS4 this evening. And the connection times out just the same as it has with the Switch earlier in the day.
It’s not just a Switch issue.