Installing esoteric fonts on iPhone (& iPad)

Sometime in the past I successfully installed two fonts for typing Eritrean & Ethiopian languages such as Tigrinya & Amharic (the fonts I'm looking for are gf zemen & abyssinicasil) on my iPad, but I've been unable to recall how or to successfully do the same on my iPhone 6s. I've been able to locate both fonts in searches, but they appear to be only available for Mac & Windows. Can someone advise me as to how I can load these fonts on my phone (& also on my newer iPad)?

Thanks

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