I would build your own router if you have any security concerns.
You can build from suitable hardware but even the Chinese built 'mini-PC' style devices are able to use Open Source BIOSs and firmware such as Coreboot which is the same as APU devices from PC Engines.
There are great router/firewalls you can use from OpenSource such as PFSense, OPNSense and Untangle (which is not free though).
IMO BT are probably worse from a security perspective although their rationale for installing remote access to their supplied equipment is from a customer support perspective rather than anything nefarious but could still be misused.
OPNSense on APU2 + Wireguard
PiHole + unbound