Welcome to the forums.
How much RAM does your computer have? If 2GB or less you seriously have to consider buying an upgrade to 4GB in the very least. Because at least half the Linux OS's will ask for at least 4GB RAM. 1GB will not be good enough anymore, and 2GB will be enough for 32-bit but is not considered secure anymore for web browsing.
Otherwise try live distros for yourself. There are a few that look enough like MacOS, but don't be bought only by appearance. Make sure you are comfortable enough with it. Don't try one distro and then decide to install it to stay with it for life because "I don't want to waste my time". If you really don't have a lot of time, try three of them, in sessions of a few hours or what you can. Don't install anything unless you're absolutely sure and you're comfortable with it.
Ubuntu is top-heavy these days. It comes with a variety of desktop environments called "flavors". The distro just called "Ubuntu" comes with GNOME, which is less configurable than other desktops but offers an elegant, modern feel. It depends on years-long users of MacOS but it might be the best choice for them. The heavyweight alternative is KDE which could be made to look more like Windows. Both environments however, want a lot of memory and system resources. There are other desktop environments like LXQt and XFCE which could also look good and don't demand as much memory but might not be suited to your taste. If you really dig desktop animations you certainly would do well to get as much RAM as you can for your ageing personal computer.
Of course there are other distros around, but I only mentioned Ubuntu since it's the most popular one.