add back feature flag

src/components/FeatureFlagModal/FeatureFlagModal.tsx

 import { BaseVariant, FeatureFlag, featureFlagSettings, useUpdateFlag } from 'featureFlags'
+import { useFiatOnrampFlag } from 'featureFlags/flags/fiatOnramp'
 import { LandingRedirectVariant, useLandingRedirectFlag } from 'featureFlags/flags/landingRedirect'
 import { Permit2Variant, usePermit2Flag } from 'featureFlags/flags/permit2'
 import { TraceJsonRpcVariant, useTraceJsonRpcFlag } from 'featureFlags/flags/traceJsonRpc'
@@ -215,6 +216,12 @@ export default function FeatureFlagModal() {
         featureFlag={FeatureFlag.landingRedirect}
         label="Landing Page Redirect"
       />
+      <FeatureFlagOption
+        variant={BaseVariant}
+        value={useFiatOnrampFlag()}
+        featureFlag={FeatureFlag.fiatOnramp}
+        label="Fiat on-ramp"
+      />
       <FeatureFlagGroup name="Debug">
         <FeatureFlagOption
           variant={TraceJsonRpcVariant}

src/components/FiatOnrampAnnouncement/index.tsx

 import { Trans } from '@lingui/macro'
 import { useWeb3React } from '@web3-react/core'
 import fiatMaskUrl from 'assets/svg/fiat_mask.svg'
+import { BaseVariant } from 'featureFlags'
+import { useFiatOnrampFlag } from 'featureFlags/flags/fiatOnramp'
 import { useCallback, useEffect, useState } from 'react'
 import { X } from 'react-feather'
 import { useToggleWalletDropdown } from 'state/application/hooks'
@@ -115,11 +117,13 @@ export function FiatOnrampAnnouncement() {
     acknowledge({ user: true })
   }, [acknowledge, toggleWalletDropdown])
 
+  const fiatOnrampFlag = useFiatOnrampFlag()
   const openModal = useAppSelector((state) => state.application.openModal)
 
   if (
     !account ||
     acks?.user ||
+    fiatOnrampFlag === BaseVariant.Control ||
     locallyDismissed ||
     sessionStorage.getItem(ANNOUNCEMENT_DISMISSED) ||
     acks.renderCount >= MAX_RENDER_COUNT ||

src/components/TopLevelModals/index.tsx

@@ -2,6 +2,8 @@ import { useWeb3React } from '@web3-react/core'
 import AddressClaimModal from 'components/claim/AddressClaimModal'
 import ConnectedAccountBlocked from 'components/ConnectedAccountBlocked'
 import FiatOnrampModal from 'components/FiatOnrampModal'
+import { BaseVariant } from 'featureFlags'
+import { useFiatOnrampFlag } from 'featureFlags/flags/fiatOnramp'
 import useAccountRiskCheck from 'hooks/useAccountRiskCheck'
 import { lazy } from 'react'
 import { useModalIsOpen, useToggleModal } from 'state/application/hooks'
@@ -18,6 +20,8 @@ export default function TopLevelModals() {
   const { account } = useWeb3React()
   useAccountRiskCheck(account)
   const accountBlocked = Boolean(blockedAccountModalOpen && account)
+  const fiatOnrampFlagEnabled = useFiatOnrampFlag() === BaseVariant.Enabled
+
   return (
     <>
       <AddressClaimModal isOpen={addressClaimOpen} onDismiss={addressClaimToggle} />
@@ -25,7 +29,7 @@ export default function TopLevelModals() {
       <Bag />
       <TransactionCompleteModal />
       <AirdropModal />
-      <FiatOnrampModal />
+      {fiatOnrampFlagEnabled && <FiatOnrampModal />}
     </>
   )
 }

src/components/WalletDropdown/AuthenticatedHeader.tsx

@@ -7,6 +7,8 @@ import Tooltip from 'components/Tooltip'
 import { getConnection } from 'connection/utils'
 import { getChainInfoOrDefault } from 'constants/chainInfo'
 import { SupportedChainId } from 'constants/chains'
+import { BaseVariant } from 'featureFlags'
+import { useFiatOnrampFlag } from 'featureFlags/flags/fiatOnramp'
 import useCopyClipboard from 'hooks/useCopyClipboard'
 import useStablecoinPrice from 'hooks/useStablecoinPrice'
 import useNativeCurrency from 'lib/hooks/useNativeCurrency'
@@ -226,6 +228,7 @@ const AuthenticatedHeader = () => {
     closeModal()
   }, [clearCollectionFilters, closeModal, navigate, resetSellAssets, setSellPageState])
 
+  const fiatOnrampFlag = useFiatOnrampFlag()
   // animate the border of the buy crypto button when a user navigates here from the feature announcement
   // can be removed when components/FiatOnrampAnnouncment.tsx is no longer used
   const [acknowledgements, acknowledge] = useFiatOnrampAck()
@@ -312,6 +315,7 @@ const AuthenticatedHeader = () => {
         >
           <Trans>View and sell NFTs</Trans>
         </ProfileButton>
+        {fiatOnrampFlag === BaseVariant.Enabled && (
           <>
             <BuyCryptoButton
               $animateBorder={animateBuyCryptoButtonBorder}
@@ -348,6 +352,7 @@ const AuthenticatedHeader = () => {
               </FiatOnrampNotAvailableText>
             )}
           </>
+        )}
         {isUnclaimed && (
           <UNIButton onClick={openClaimModal} size={ButtonSize.medium} emphasis={ButtonEmphasis.medium}>
             <Trans>Claim</Trans> {unclaimedAmount?.toFixed(0, { groupSeparator: ',' } ?? '-')} <Trans>reward</Trans>

src/featureFlags/flags/fiatOnramp.ts

+import { BaseVariant, FeatureFlag, useBaseFlag } from '../index'
+
+export function useFiatOnrampFlag(): BaseVariant {
+  return useBaseFlag(FeatureFlag.fiatOnramp)
+}