I didn’t read every reply, so someone may have mentioned this already. I wanted to recommend the CruisePlum website for finding solo cruising deals. There’s a search function where you can narrow down deals, for example, based on room type or region. Someone recommended the website on the Solo Cruisers category here on CC.
For the past couple of years, I have cruised mostly solo on MSC and have yet to pay a single supplement. I cruised solo on a 10-day S. Caribbean on Celebrity in September and my single supplement fare was about 10% . MSC was just starting in the US market when I first started solo cruising and then COVID happened, so both of those things may have caused me to have good fortune in booking solo deals. For instance, I booked a 25-night cruise TA to the Caribbean AND Europe for May. I used a 30% off coupon which I got from playing poker games on an iPhone app (no money, just playing for fun), so I DID have some help, but the total for a solo, balcony room, was around $1700, with $500 OBC.
I hope you will continue to cruise, as a solo. I cruise for the same reasons you do: the solitude of a balcony room is wonderful, but if I feel sociable, I have several choices just outside my door. I gain a sense of pride for doing things in port that I never thought I would do without a partner. I mean group excursions, not exploring on my own. I’m adventurous, not foolish. 😉