One workout to throw into the mix:
90s at 10k pace, 30s at mile pace, times 10.
It's 20 minutes of toughness. Can be done by yourself on a nice dirt trail, so you aren't suffering around a track solo.
Out 10 easy, back in 8 minutes, repeat, then cool down.
About 50 minutes of total running, easier to do by yourself than a 20 minute tempo would be.
Mile-quarter workout: a road/dirt mile in a bit slower than 5k pace, then 2 minutes walking rest, then a quarter faster than mile pace, 5 minutes rest, 3 to 4 total sets. I used to do this in college. I was more of an 800 guy so was consistently surprised how hard the mile felt (usually tried for just under 5) and how painful but fast the quarter could be ( usually about 60 for the first one and would be down about 56 for the last one).
There are three workouts thst I think would be easier to do alone than slogging through repeats on the track, which I find really lonely by yourself.
I find taking any track workouts and getting them onto fast a fast grass or dirt course with a fair bit of turning and trees to block my view of the entire repeat helps mentally a lot if I'm alone.