How easy and expensive would it be to swap this with US English?

On the T14 (not T14s) it is easy. See https://support.lenovo.com/us/en/videos/nvid500443-replacing-your-keyboard-thinkpad-t14-and-p14s-gen-1-and-2-customer-self-service
Seems to be available from ~30USD https://www.amazon.com/Replacement-Keyboard-5N20V44072-5N20V43774-5N20X68864/dp/B0B3RV3LK5
ifixit has genuine parts for ~75USD https://www.ifixit.com/products/5n20v44072-lenovo-laptop-keyboard-genuine

Only thing I dislike about the T14s is that you have to dissassemble everything to replace the keyboard. On the T14 it’s so much easier.

A refurbished Lenovo T14 or T16 should do it.

While I’m morally in the opnsense camp I know pfsense has more third party packages available.
Running docker in an lxc sounds interesting, I’m a bit old school and enjoy the isolation that a true vm gives you.

Router: opnsense/pfsense
Switch: I guess look at something like Open vSwitch After some more reading I would go for a proprietary managed switch here. WiFi/Mesh network: OpenWrt with 802.11r setup - https://openwrt.org/docs/guide-user/network/wifi/roaming
Server: Proxmox or Debian Bookworm with KVM/Qemu
Docker/Kubernetes: Portainer CE version as a VM in Proxmox - https://github.com/portainer/portainer
Collab software: https://github.com/nextcloud/server
Server Backup: Proxmox backup server or Borg backup/Restic
Client backup: Borg backup/Restic

Most of my data are on 2x16TB HDDs running an mdraid1 and then I backup it all to a usb drive with Borg Backup.
The os.qcow2 files live on my m.2 NVMe and are manually backuped to the mdraid1 before running the borg backup.
I should automate the borg backup but currently I just do it manually a few times a month.
Would also like to have two usb drives and keep one offline in another part of the house but that’s another future project.