The hardware architecture is “MIPS 32bit little endian” (mipsel for short) but Go toolchain calls it mipsle (tailscale is written in Go). More here https://superuser.com/questions/1262144/naming-mipsle-vs-mipsel.
Follow https://tailscale.com/kb/1053/install-static/ tutorial.
cd /root https://pkgs.tailscale.com/stable/tailscale_1.32.2_mipsle.tgz tar zxvf tailscale_1.32.2_mipsle.tgz
tailscale needs iptables. The firmware ships it as /system/bin/xtables-multi.
mkdir /root/bin cp /system/bin/xtables-multi /root/bin export PATH=$PATH:/root/bin
/root/tailscale_1.32.2_mipsle/tailscaled --state=tailscaled.state & /root/tailscale_1.32.2_mipsle/tailscale up
The last command will print a URL to open for authentication.