Running lightning in prune mode
It is possible to run Lightning (both LND and c-lightning) with bitcoind pruned mode.

There are already packages turning the pruned mode on when disk space is limited: Lightning Power Node Launcher (works with LND) and BTCPayServer docker (works with c-lightnig).

There is a lot of conflicting information online, because it became possible only after Bitcoin Core 0.16.0 was released.

Update from the official lnd documentation:


  We don't require --txindex when running with bitcoind but
  activating the txindex will generally make lnd run faster.
  
  NOTE: WE DO NOT FULLY SUPPORT PRUNED OPERATING MODES FOR FULL NODES.
  It's possible to run a node in a pruned mode and have it serve lnd,
  however one must take care to ensure that lnd has all blocks on disk
  since the birth of the wallet, and the age of the earliest channels
  (which were created around March 2018).