Can't change the proxy admin because of "Error: Proxy admin is not the one registered in the network manifest"

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This may be related to your other thread: upgradeProxyAdmin is not changing the ProxyAdmin of my Proxies - #2 by ericglau

If your proxy admin is an EOA rather than a ProxyAdmin contract, you would need to use that EOA to call changeAdmin directly on the TransparentUpgradeableProxy.