My suggestion would be Audacity’s native “Delay” effect followed by stereo (not mono) reverberation effect.
The YouTube example you linked to has a Tannoy (public-address) quality, rather than cathedral, if you want the public-address effect you’ll need to use a narrow-band equalization before you do anything else, (see “AM radio” / megaphone effect).
If you are really fussy the echoes from created by the delay effect should have their high-frequency content progressively cut to simulate what would occur in reality.