LinkedIn Ads are brutal for anything mobile-first. Even for B2B app installs, the CPMs are ridiculous and you end up paying for a lot of bot traffic. For a bootstrapped startup, it's basically throwing money away.
Meta works if you're going after a broad B2B SaaS audience - think project management or HR tools. But the moment you niche down to something like "VC partners in climate tech," performance tanks. No amount of lookalikes or tight forms will save you. I've seen it happen dozens of times.
Google is the workhorse. PMax and Search still deliver consistent results for app install campaigns too, especially if you optimise for in-app events. The targeting might be less surgical, but the intent is real.
All depends on your offer, creatives, and what you're optimising for - brand lift, instal volume, or downstream conversions. Your mileage will vary.