Hey folks! Thanks for adding support for React 17 and 18, it's much appreciated!

However, there are a couple of warnings when installing eui with react 18:

npm WARN ERESOLVE overriding peer dependency
npm WARN While resolving: react-element-to-jsx-string@14.3.4
npm WARN Found: react@18.2.0
npm WARN node_modules/react
npm WARN peer react@"^16.12 || ^17.0 || ^18.0" from @elastic/eui@87.0.0
npm WARN node_modules/@elastic/eui
npm WARN peer @elastic/eui@"^87.0.0" from the root project
npm WARN 83 more (@emotion/react, ...)
npm WARN
npm WARN Could not resolve dependency:
npm WARN peer react@"^0.14.8 || ^15.0.1 || ^16.0.0 || ^17.0.1" from react-element-to-jsx-string@14.3.4
npm WARN node_modules/@elastic/eui/node_modules/react-element-to-jsx-string
npm WARN react-element-to-jsx-string@"^14.3.4" from @elastic/eui@87.0.0
npm WARN node_modules/@elastic/eui
npm WARN
npm WARN Conflicting peer dependency: react@17.0.2
npm WARN node_modules/react
npm WARN peer react@"^0.14.8 || ^15.0.1 || ^16.0.0 || ^17.0.1" from react-element-to-jsx-string@14.3.4
npm WARN node_modules/@elastic/eui/node_modules/react-element-to-jsx-string
npm WARN react-element-to-jsx-string@"^14.3.4" from @elastic/eui@87.0.0
npm WARN node_modules/@elastic/eui
npm WARN ERESOLVE overriding peer dependency
npm WARN While resolving: react-element-to-jsx-string@14.3.4
npm WARN Found: react-dom@18.2.0
npm WARN node_modules/react-dom
npm WARN peer react-dom@"^16.12 || ^17.0 || ^18.0" from @elastic/eui@87.0.0
npm WARN node_modules/@elastic/eui
npm WARN peer @elastic/eui@"^87.0.0" from the root project
npm WARN 49 more (@floating-ui/react-dom, @hello-pangea/dnd, ...)
npm WARN
npm WARN Could not resolve dependency:
npm WARN peer react-dom@"^0.14.8 || ^15.0.1 || ^16.0.0 || ^17.0.1" from react-element-to-jsx-string@14.3.4
npm WARN node_modules/@elastic/eui/node_modules/react-element-to-jsx-string
npm WARN react-element-to-jsx-string@"^14.3.4" from @elastic/eui@87.0.0
npm WARN node_modules/@elastic/eui
npm WARN
npm WARN Conflicting peer dependency: react-dom@17.0.2
npm WARN node_modules/react-dom
npm WARN peer react-dom@"^0.14.8 || ^15.0.1 || ^16.0.0 || ^17.0.1" from react-element-to-jsx-string@14.3.4
npm WARN node_modules/@elastic/eui/node_modules/react-element-to-jsx-string
npm WARN react-element-to-jsx-string@"^14.3.4" from @elastic/eui@87.0.0
npm WARN node_modules/@elastic/eui
npm WARN ERESOLVE overriding peer dependency
npm WARN While resolving: react-input-autosize@3.0.0
npm WARN Found: react@18.2.0
npm WARN node_modules/react
npm WARN peer react@"^16.12 || ^17.0 || ^18.0" from @elastic/eui@87.0.0
npm WARN node_modules/@elastic/eui
npm WARN peer @elastic/eui@"^87.0.0" from the root project
npm WARN 83 more (@emotion/react, ...)
npm WARN
npm WARN Could not resolve dependency:
npm WARN peer react@"^16.3.0 || ^17.0.0" from react-input-autosize@3.0.0
npm WARN node_modules/@elastic/eui/node_modules/react-input-autosize
npm WARN react-input-autosize@"^3.0.0" from @elastic/eui@87.0.0
npm WARN node_modules/@elastic/eui
npm WARN
npm WARN Conflicting peer dependency: react@17.0.2
npm WARN node_modules/react
npm WARN peer react@"^16.3.0 || ^17.0.0" from react-input-autosize@3.0.0
npm WARN node_modules/@elastic/eui/node_modules/react-input-autosize
npm WARN react-input-autosize@"^3.0.0" from @elastic/eui@87.0.0
npm WARN node_modules/@elastic/eui

Which is a really long way of saying react-input-autosize only supports peer react@"^16.3.0 || ^17.0.0" and
react-element-to-jsx-string only supports peer react-dom@"^0.14.8 || ^15.0.1 || ^16.0.0 || ^17.0.1".

Which appears to be right, react-input-autosize doesn't support it at all (there's a fork tho):
JedWatson/react-input-autosize#196
and you need react-element-to-jsx-string to be on v15