Fellow minimalist here. While I’ve owned a good number of ukuleles in total over the years, I have successfully held myself to 1-2 at a time. I’ve been in your shoes and I’ve had to think very hard about my motivation for keeping the ukulele: function or sentimentality. If my motivation is sentimental and I let the instrument go, I rarely miss it after a short adjustment period.
There are many good functional reasons to keep a ukulele that have been mentioned in this thread (high g/low g for example), so I won’t wade into those waters. What I will say is that it sounds like you might be trying to find a functionality based justification for a sentimental attachment. It seems like that could be the root of the internal tension.
I have a solution to propose that has worked for me. Don’t sell it, but also don’t keep it. As long as the dollar value of the instrument won’t make or break you, gift it to someone in your life who would find it meaningful. If you have a fleeting moment of missing the instrument afterward, you’ll be reminded that you shared that joy with someone else.