Hi @roman_r_m,
It seems I am running ipv6 and ipv4 simultaneously. It does look like ipv6 has given others problems as well:
Priority of IPv4 and IPv6 addresses in Linux version?
Connecting Joplin to a IPv6 sync target
Joplin sync failure on IPv6 only networks
Joplin sync failure on IPv6 only networks
Of note, however, I was able to sync Joplin after disabling my VPN (I use Private Internet Access). Although, after reactivating the VPN, my sync configuration check produced the original error again. I can still sync Joplin while running my VPN without issue on my iPad Pro, MacBook Pro, and even another laptop running Linux Mint.
What do people think?
Any further ideas or recommendations are highly appreciated.
Thank you.