The pool class implements two methods which are equivalents: actor() and get():
https://searchfox.org/mozilla-central/source/devtools/shared/protocol/Pool.js#99-114
https://searchfox.org/mozilla-central/source/devtools/shared/protocol/lazy-pool.js#27-43

protocol.js and newest code use actor(), whereas old legacy code uses get().
We should identify all the usages of get() in order to call actor() instead.

There is at very least all of these cases:
https://searchfox.org/mozilla-central/search?q=pool.get(&case=false&regexp=false&path=devtools%2F

But there might be lots of hidden usages, which won't only be on the actor side as Pool class is being inherited by Front and Actor classes:
https://searchfox.org/mozilla-central/search?q=%5C.get%5C(.*id%5C)&case=false&regexp=true&path=devtools%2F
By scanning quickly this list, I found:
https://searchfox.org/mozilla-central/source/devtools/client/accessibility/provider.js#34
https://searchfox.org/mozilla-central/source/devtools/client/inspector/grids/grid-inspector.js#211 (may be?)
https://searchfox.org/mozilla-central/source/devtools/server/actors/thread.js#1486
https://searchfox.org/mozilla-central/source/devtools/server/actors/thread.js#1747
https://searchfox.org/mozilla-central/source/devtools/server/actors/webconsole.js#617
https://searchfox.org/mozilla-central/source/devtools/server/main.js#1200
https://searchfox.org/mozilla-central/source/devtools/shared/client/debugger-client.js#928
https://searchfox.org/mozilla-central/source/devtools/shared/fronts/inspector.js#106
https://searchfox.org/mozilla-central/source/devtools/shared/fronts/inspector.js#292
The goal here is to find all usages of get function on anything that is Pool, Actor or Front.