Reducing crackles from old audio clip

Hi there, I am a total newbie to this sound world and need some help.
There is a huge audio clip of almost 3 hours (I have attached a part of them) which I wish to make a bit more audible.
Original audio clip is file aud1 and things which I have tried so far on standard settings are Noise reduction, Declicker, de-esser and vocal isolation.
Still the resultant is not very good and satisfactory as there is a lot more crackles while the main content is being spoken (no idea whats that called).
Please do help me if you can as this is my grandfather’s birthday present. file:///home/yashashwi/Music/2cd0%20New%20folder%20sodash/aud1.wav

That was unsuccessful: here’s a link to instructions on how to attach audio to a post in this forum …

If there is more noise than signal, then I would not get your hopes up that it can be made comprehensible.
[The audio-recovery shown in movies & TV-shows is often impossible science-fiction].

Really sorry for not attaching it properly, here we go

If you filter-out everything above 4kHz, and everything below 200Hz, it sounds less harsh

You can filter those out with an equalizer, or high/low-pass filters.

[IMO the bubbly digital-artefact noises are impossible to remove].

Are there any more things i should try as the resultant audio is still pretty weak.

spectral editing to remove the most intrusive of the artefact noises …
spectral editing.gif