I still have my normal L2TP service with @aaisp - but I route it via WireGuard. So I'm tunneled twice. This lowers my overall MTU, but mitigates these issues:
* My local ISP (main one) is a bit funny about L2TP, often throttles it
* xl2tpd / a&a's L2TP server is a bit slower about failover; when my client IP changes, my L2TP is down for a minute, when switching to backup internet
Routing L2TP through wireguard mitigates both issues. wg-quick reconnects within seconds, during failover.