I can confirm, it seems to be related to DNS blocking (I also run PiHole). Whitelisting the following two domains seems to have helped:
vortex.data.microsoft.com
xboxlive.com.akadns.net
We also have this problem on different iOS devices: iPhone 11, iPad Pro 12.9" (2. Generation), iPad 9" (6. Generation)
I have attached the logs of three subsequent crashes. All seem to relate to http-requests made from the XBox-Service. Hopefully just a faulty JSON that is causing the problems...
[media][media][media]
On iOS (which also crashes since the latest update when signed in to a microsoft account, see MCPE-96184) the crashes are produced by DNS-Blocking (e.g., PiHole). Unblocking some Microsoft domains (vortex.data.microsoft.com and xboxlive.com.akadns.net) seems to be a workaround. Maybe that helps on the switch version as well...