Does TDM work in both directions? I will assume you are trying an IP connection when both Macs are in Mojave.
If you are in System Preferences on either machine, do you see the Thunderbolt Bridge?
Part 1...
My setup
2013 rMBP with W10 installed (on macOS Sierra.6).
bridge0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=63<RXCSUM,TXCSUM,TSO4,TSO6>
ether 72:00:00:7d:a3:10
inet6 fe80::1c9c:1b89:2054:dd33%bridge0 prefixlen 64 secured scopeid 0x9
inet 169.254.15.174 netmask 0xffff0000 broadcast 169.254.255.255
Configuration:
id 0:0:0:0:0:0 priority 0 hellotime 0 fwddelay 0
maxage 0 holdcnt 0 proto stp maxaddr 100 timeout 1200
root id 0:0:0:0:0:0 priority 0 ifcost 0 port 0
ipfilter disabled flags 0x2
member: en1 flags=3<LEARNING,DISCOVER>
ifmaxaddr 0 port 5 priority 0 path cost 0
member: en2 flags=3<LEARNING,DISCOVER>
ifmaxaddr 0 port 6 priority 0 path cost 0
nd6 options=201<PERFORMNUD,DAD>
media: autoselect
status: active
2018 Mini (Mojave.4 connected via USBc-to-TB2 adapter to the 2013 rMBP.
bridge0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=63<RXCSUM,TXCSUM,TSO4,TSO6>
ether 3a:00:28:18:6f:01
inet6 fe80::1c88:38ed:a72:41fb%bridge0 prefixlen 64 secured scopeid 0x12
inet 169.254.58.44 netmask 0xffff0000 broadcast 169.254.255.255
Configuration:
id 0:0:0:0:0:0 priority 0 hellotime 0 fwddelay 0
maxage 0 holdcnt 0 proto stp maxaddr 100 timeout 1200
root id 0:0:0:0:0:0 priority 0 ifcost 0 port 0
ipfilter disabled flags 0x2
member: en2 flags=3<LEARNING,DISCOVER>
ifmaxaddr 0 port 14 priority 0 path cost 0
member: en3 flags=3<LEARNING,DISCOVER>
ifmaxaddr 0 port 15 priority 0 path cost 0
member: en4 flags=3<LEARNING,DISCOVER>
ifmaxaddr 0 port 16 priority 0 path cost 0
member: en5 flags=3<LEARNING,DISCOVER>
ifmaxaddr 0 port 17 priority 0 path cost 0
nd6 options=201<PERFORMNUD,DAD>
media: autoselect
status: active