Apple syncs between your own Apple devices and services, but what about other devices and online services? To enable you to sync everywhere else and to anything, there is SyncMate for macOS.
Apple iCloud does a good job of syncing contacts, calendars, photos, documents and other data between the Macs, iPhone and iPads you own. You can pick up any computer or device you are logged into and everything is there.
That is fine and it works well, but there are many other devices and online services that you may be using and syncing with them may present difficulties or require extra software. For example, you may use Google Drive, OneDrive, Dropbox, an Android phone or tablet, and other non-Apple devices and services.
There are apps for most of those, but then you end up with multiple apps on your Mac syncing files. They use storage, memory and processing power, so you might not want to run them all at the same time. Some devices may not have apps and none is provided with an Android phone to connect it to a Mac and sync files for example.
SyncMate aims to be one sync app to rule them all. Instead of using an app for each service, SyncMate does them all. This could be lighter on the Mac’s resources and it is one central place in which to control all your syncing.
Sync with online storage

The sidebar contains a list of connections and is initially empty. Clicking the Add new item provides a choice of nine connection types, such as Android Device, iOS Device, Another Mac, Mounted Device, Dropbox, Google Account, MTP Device and others.
Select Google Account for example, and you can choose what you want to sync, such as Calendar, Contacts, Folders, and more. If you choose to sync folders, a folder on the Mac and a folder on Google Drive are selected. It can handle multiple pairs of folders and sync the contents of them.

A sync direction can be set, which can be one way Mac to remote device/service or remote to Mac, or two way. It depends on the syncing, but there may be an option to choose how to resolve conflicts, like choosing whichever file is newest. Filters and exclusions can be created if there are files you don’t want to sync, and it can ignore hidden files and folders if you want.
I synced with a folder on Google Drive and it worked fine. There were a lot of folders, subfolders and files, but even so, I thought it was a bit slow. It did it eventually though.
Sync Mac and Android devices
Syncing with your iPhone and iPad is best left to iCloud, but there are no facilities for syncing with an Android phone or table in macOS. SyncMate adds the sync feature you need. (I looked at MacDroid here, which syncs Macs and Android phones.)

If you choose to sync an Android device, SyncMate offers three options, USB, Wi-Fi and Bluetooth. To sync wirelessly requires an app to be installed on the phone from SyncMate. I prefer not to install apps outside of the Google Play Store and plugged in my old Samsung phone running Android 7.
I initially had some problems connecting it, but solved them by installing FUSE for macOS which extends Mac support for alternative filing systems and by selecting an MTP Device for the connection type. This is a connection and transfer protocol that enables files, especially media files, to be transferred between devices.

Folders, photos and music can be transferred between the Mac and the Android device and once the connection is established, it works like any other connection. You choose folders to sync and the sync direction. For example, I chose to sync the phone’s DCIM folder containing photos and videos to a folder in the Mac’s Documents folder. It synced OK, although a bit slowly.
Summing up
SyncMate is available for free, although the sync options are limited to calendar and contacts. To sync folders and files requires the Expert edition costing US $39.95 (UK £37.52).
An Expert edition reg code was provided so I could try the extra features. I did not try every possible sync combination, but I tried some, such as syncing with Google Drive and an Android phone and they worked fine, but a bit slow.
SyncMate could be used to replace several third party sync apps like Dropbox and Google Drive, and add Android and MTP device support. It is a bit more flexible in that any local folder can be synced with any remote folder. However, don’t install SyncMate from the Mac App Store, that is an outdated version. Get it from the SyncMate website.