I don't have personal experience with rowers, so I can't speak to that other than to say the concept2 is what everybody recommends.

Regarding indoor bikes, personally I think they are great. The two that are generally recommended are Schwinn Airdynes and the Assault Bike. I have an AirDyne (model AD6 if you care) that I am happy enough with considering I bought it used for $200 off FB marketplace. If I were to buy new, I would go with the Assault Bike, hands down. I have used both and the AirDyne is fine, but the Assault Bike is truly BIFL. It is a tank. I do not do CrossFit, and think an indoor bike is a great cardio staple for a variety of goals.

And because I saw Bowflex adjustable dumbbells mentioned elsewhere, I will throw out my 2 cents there - I recommend ironmaster. For adjustable dumbbells, the most common recommendations are Bowflex, Power blocks, and Ironmaster. Ironmaster is by far the most durable, but also take the longest to change weights and have the largest footprint. Since you are in r/BIFL, I would recommend the Ironmasters. I've had mine for about 4 years, and the only issue I've had is the paint can chip off the weights if you clank them together too hard.

I feel like you're on the right track with the rower/assault bike. If you already have a squat rack and weights, how about a bench, adjustable dumbbells, kettle bells, etc? I can provide recommendations if you're interested in going down that path.