If you didn’t have any problems running 1.3.5 then you’re probably fine as we were coming from a relatively old version of VyOS.
As for the sources.list, using the packages for the rolling release isn’t going to work since we are using VyOS 1.3.6 at the moment. The problem with simply installing linux-perf is related to the latest blog post and topics like Unable to build ISO 1.4
In regards to the workarounds, VyOS 1.3.6 is using FRRouting (version 7.5.1-20231128-03-g06f8c4ce0) and it doesn’t know the command zebra nexthop-group keep 1. We are also unsure at the moment if raising the dplane limit would help, since we would expect this to be a problem to be encountered right after starting the BGP daemon.
What we know right now is, that it is not only a problem with an IXP but with IPv6 BGP, zebra and maybe the kernel in general. By shutting all the IPv6 BGP sessions, we seem to be able to get rid of the (IPv4 and IPv6) lag spikes. We can even reenable some sessions and the problems are temporarily gone.
We are currently considering upgrading to VyOS 1.4.0-epa2, even though we already encountered several problems with the migration of the configuration. The whole firewall configuration is gone after going from 1.3.6 to 1.4.0-epa2. Besides that, a policy route is missing and all our route-maps that set a community are broken, since the communities are not there anymore. We are checking for more problems soon and will share our finding in the development portal.