Good points well made.
Depends what budget and expenditure the OP is comfortable with.
Re the one UWA prime. It is a limiting choice in some ways...but it also makes you work hard
For instance I reckon for just my area I could do a lot with just that lens alone. Let me demonstrate what a full frame camera with one 20mm prime and you can tell me just how limiting you think it would be. I guarantee you this - if the OP turned up to a workshop with an A7r4 and a 20mm lens, I could give them a whole days photography...
Just my local patch over a 7 month period in 2018 with a D810 and 20mm F1.8.
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I am not saying I would want that as my only lens for ever and ever...but I reckon I could make it work for a period.
If you feel you need longer take it portrait if the sky is epic, crop it square...lots of creative opportunities with just a 20mm