OpenVPN
Increase systemd service process limit
resolvconf ends up calling itself several times due to subscriber scripts and may go over 10 processes, resulting in the below message and ultimately an empty resolv.conf:
/bin/resolvconf: fork: retry: Resource temporarily unavailable
Hmm, I wonder whether it makes sense to increase this value or whether we should just remove it entirely. It is clearly a value that depends very much on the individual setup, especially which user openvpn is running under. 10 is probably a value that was chosen to be "high enough that it doesn't usually cause problems". To be fair, I haven't seen any other reports about this, so in most cases it seems indeed to work fine. (at least in older versions)
In my case, openvpn is the only thing running under its user. However, if the decision is to increase rather than remove the limit, I suspect it should be TasksMax=N (limited per service) rather than LimitNPROC=N (per user, as you mentioned).