how to activate BIP148 in bcoin configuration I cannot find any documentation about activating BIP148 on a bcoin node. Is there anything similar to BIP151=true in the bcoin.conf or is it enabled by default?
You can Update their node software to a BIP148-enforcing version; or
Run a BIP148 border node to filter out invalid blocks, and update their existing mining software to produce blocks with version 1 bit enabled, to vote for Segwit activation.
Signed binaries can be downloaded at BIP148 

First, install all necessary dependencies which are mentioned in the official Bitcoin build instructions details UASF