AI CS3 - CS5/C5.5 are able to open FH7 - FH11
AI CS6 - CC are unable to open FH files, but you can do it if you get the FHImport interface plugin, as well as a copy of the original FHImport plugin.
You can read on here:
If you have, or can obtain, a valid licence/legal ownership to/of any of the versions CS3, CS4, CS5, or CS5.5 (the last one is the suite), you can (download and) use that, directly or to get the original plugin.
For the possible download, you may follow the instructions here (easiest if it is registered with Adobe already):
I could install Illu CS 5.5 on my Mac, but will it run under macOS 10.14.6?
You could just try it. But don't be surprised if it doesn't work properly ...
Thanks 🙂 Your answer appeared when I had posted my reply …
What currently holds me from purchasing the Tensai plugin is this part of the (IMNVHO extremely rigid) License Terms and Conditions:
[…] the FreeHand plugin will not run under any future operating system that does not support 32 bit executables.
I was just about to purchase it to convert several dozens of old FH files when I saw this. I still have lots more old FH files on external drives but I can’t currently devote time to convert them all.
In case this is a crucial part of your progress, I'd recommend to purchase an "old" system that fully supports the Illustrator versions that are capable to passably import .fh files.
Some people on the forums might still have the older versions, so if it's only a few files, upload them to Dropbox or the like and post a link here.
If you have a lot of files, you would either need to find solution you can install yourselves or find a conversion service.
BTW, after reading the above information, I had installed a macOS 10.14 virtual machine just for being able to use the Tensai plugin, which, at the time, was said not to get a 64 bit update (at least that was how I understood it).
But when I opened that virtual machine today and wanted to install Illustrator and the Tensai plugin for converting my old FreeHand files, I was very delighted to learn that Tensai did actually update the plugin for 64 bit, see https://www.tensai.co.uk/ai/support.php:
Announcement October 27 2019 Since we first released our FreeHand plugin in July 2014, the purchase of a license was for the license only and did not include any commitment to support or upgrade of the plugin. We have been providing free email support and upgrades as a business courtesy to our customers since then. Until today, the terms and conditions customers agreed to when purchasing a license and installing the plugin stated that "the FreeHand plugin will not run under any future operating system that does not support 32 bit executables". When these terms and conditions were drafted, we did not anticipate either Apple or Microsoft removing support for 32 bit executables in the short or medium term. In September 2017, we learnt that Apple was planning to discourage the use of 32 bit apps in the next version of Mac OS (Mojave) and then remove support completely in the following version (Catalina). At this point we froze the price of the plugin and began attempting to create a 64 bit version of the plugin. We are pleased to announce that the 64 bit version of the plugin has now been released. Due to the amount of development work involved and also the fact that the price of the plugin has been frozen for 3 years, we have increased the price of the plugin and implemented an email support and upgrade subscription plan. From today, when you purchase a license for the plugin it will include email support and upgrades for one year and you will be offered the option of signing up to an ongoing yearly paid subscription. Customers who have already purchased a license will also be given one year of free email support and upgrades from the date the license was purchased. If the license was purchased more than one year ago it will not include any further email support or upgrades. Customers can purchase a subscription for existing licenses using their license key in our online shopping cart.